A 22-year-old Arizona man has been charged over the shooting in the United States in which which six people were killed and a congresswoman critically wounded.
Jared Lee Loughner has been charged with five criminal counts, including attempted assassination.
He is accused of opening fire with a semi-automatic pistol as Gabrielle Giffords was holding a constituency meeting outside a supermarket in Tucson on Saturday.
The Democratic congresswoman was shot in the head. Among the six people killed were her senior aide, a US federal judge and a nine-year-old girl. Twelve others were wounded.
Jared Loughner was tackled to the ground and arrested at the scene of the shooting.
Police released CCTV footage of a second man they wanted to question, but Pima County sheriff Clarence Dufnik said it subsequently appeared that person may not have been involved.
FBI director Robert Mueller said there was no information at present to suggest any specific threat remained.
Doctors cautiously optimistic
Ms Giffords, 40, remained in critical condition but surgeons at the Arizona University Medical Center said they were cautiously optimistic, especially since the bullet that hit her had not crossed both hemispheres of the brain.
A single bullet traveled the length of her brain on the left side, doctors at University Medical Center said.
Transfusions had worked well and the congresswoman was able to respond to simple commands after surgery, they said.
Dr Peter Rhee said it was "as good as going to get" but the situation was was still very precarious.
Given the devastating nature of the wound, doctors said they were uncertain about the extent of damage to the brain Ms Giffords had suffered.